Electroplating



Patented Apr. 24, 1945 anac'raomrmc mm '0. Hull, In-kewood, Ohio, m w a. 1. du Pont de Nemonra I; Company, Wilmington, Del., a corporation (if-Delaware 80 Drawing.

Application September (I, 1941, sci-u No.- maszs I 2 Claims. (c1. 204-52) This invention relates to the electrodeposition of copper from acid baths and is more particularly directed to 'electrodepositing compositions and processes wherein cuprous cyanide is employed as an addition agent in acid-copper baths. The invention is further directed to articles comprising cuprous cyanide by use of which cuprous cyanide may conveniently be added to electrodepositina baths.

Copper, and its alloys. may be electrodeposited from either acid or alkaline baths. The alkaline baths, especially cyanide, have been preferred for electroplating because of the better character of deposit obtainable and because of the more desirable operating characteristics. Alkaline copper baths cannot satisfactorily be used for electroforming, electrotyping or electrorefinin'g, however, because of the dimculty of forming heavy deposits. Acid copper has therefore been used for these mirposes despite the formation of deposits that are rough and unsatisfactory.

It is an object of the present invention to provide an addition agent for acid-copper electrodepoaiting baths whereby A creased usefulness It is a further object of the invention to provide compositions and processes by means of which deposits of improved character maybe produced from acid-copper electrodepositing systems. It is a still further object toprovide acid-copper electrodepositing compositions and processes which are inexpensive and which require a minimum of maintenance for satisfactory use. -It is a still further object to provide articles comprising cuprous cyanide by the use of which cuprous cyanide may readily be added to electrodepositing baths. Still i'ur ther objects will become apparent hereinafter.

I have found that the foregoing and other obiects of the invention are attained by the use of cuprous cyanide as an addition agent in aci'dcopper electrodepositing baths. Cuprous cyanide causes the deposits from acid-copper baths to be smooth, ductile, and builable and does not impart undesirable brittleness to deposits. Cuprous cyanide, surprisingly enough, also exercises the unexpected effect of minimizing anode sludge formation. This is of particular importance in such ent invention cuprous cyanide is quite stable and it does not, as might be expected, break down with the evolution of the exceedingly dangerous lrvdrocyanic acid gas.

Cuprous cyanide may be used as an addition agent according to the present invention in any acid bath for the electro-depositing of copper.

It may, for instance, be used in any of the numerous acid baths known for the electroplating, electroforming, or electrorefinlng of copper. Such baths ordinarily contain copper in the form of any of its salts such as copper sulfate or copper sulfamate, acetate, or chloride. A proper pH is maintained by the use of a suitable acid such as the baths will be of in- 85 tact with the bath by sulfuric acid, or sulfamic, acetic, or hydrochloric acid.

,The amount of cuprous cyanide to employ in a particular acid-copper electrodepositing bath is ordinarily the maximum which is soluble in the bath. About 0.1 gram per liter of cuprous cyanide can be dissolved in an acid-copper bath and this amount has been found to be about an optimum, Some of the benefits of the invention can of course be obtained by the 'use of smaller amounts of cuprous cyanide.

In normal use about 0.02 to 0.05 gram per liter of cuprous cyanide needs to be added to an acidcopper bath for each twenty-four hours of operation, and this amount may be added for bath maintenance as needed. Preferably an excess of cuprous cyanide will be maintained in the bath and in this way the bath can be kept saturated with respect to cuprous cyanide throughout its operation. Cuprous cyanide may be kept in conhanging cloth bags of the material in the bath, or by keeping articles comprising cuprous cyanide in the bath.

According to the preferred practices of this invention cuprous cyanide is included in articles 40 which may be brought into contact with an elecoperations as electroretlning and electroformins.

as sludge nuclei for rough deposits are thereby avoided. Cuprous cyanide is preferably present in the bath at its maximum solubility and accordingly it may easily be maintained at optimum concentration by supplying the bath with an excess of cuprous cyanide. the addition agent dissolving in the bath as required. Despite the acid condition which prevails in the baths of the prestrodepositing bath readily to supply required cuprous cyanide. Cuprous cyanide articles may be made simply by pressing cuprous cyanide into pellets or briquettes and these may be held in the bath in suitable bags or baskets. A formed cuprous cyanide article may also be made by cast ing or pressing cuprous cyanide mixed with about an equal amount of anhydrous calcium sulfate (plaster of Paris). Formed cuprous cyanide articles may similarly be made using other binders such as finely divided sodium silicate. One may use'small amounts of sulflte cellulose waste, glue or gelatin, dextrin, corn starch, or casein as binders.

Formed cuprous cyanide articles may advantageously include organic addition agents. some porting strap or hook by means of which they may simply be hung in a bath. Awarding to a preferred practice of the invention equal parts with a little water and cast around a hook to make articles which look like the anodes of Blouch Patent 2,097,508. I

Compositions according to the present invention may be ofleredto the trade as mixtures of suitable copper compounds including appropriate amounts of cuprous cyanide. Alternatively and preferably, cupr'ous cyanide will simply be offered formed, with or without the aid of a binder. on a support by means of which it may be suspended in a plating bath. p

In order that my invention may be better understood reference should be had to the following illustrative examples:

Ezample I An acid-copper platingbath was made up as follows: I

Copper sulfate crystals (CuBO4-5H20) g./l 150 Sulfuric acid (66 Be.) g./l 50 Cuprous cyanide (CuCN) -g./l.. 9.1 Temperature .30.. 25-30 Copper deposits made from this bath were 01 greatly improved character over similar deposits made from a bath omitting the cuprous cyanide. The cuprous cyanide was introduced into the bath by suspending in it a plaster of Paris rod in which was incorporated about 50 per cent by weight of cuprous cyanide. During operation of the bath cuprous cyanide was dissolved as required, permitting the use of ,'high current densities of about 50 A/s.f. with elimination of roughness or nodular deposits in thicknesses up to .02 inch. The extreme smoothness and line texture of deposit made the deposits easy-to bull and suitable as a base coating for nickel plating. The inclusion of about one to two grams per liter of quinone as an organic addition agent was found desirable.

Example I! An acid-copper electroreflning bath was prepared as follows:

Copper sulfate crystals csarrrrosni cn-coaiiscnos.

I Patent Io. 237L289.

oi! cuprous cyanide andplaster of Paris are mixed i Deposits made from this bath in extreme thicknesses of one-half inch were smooth and dense. In contrast to gelatin or glue which polarise the anode or cathode as much as .19 volt at 15 A/s. f. as measured by the Haring cell with resultant increased power costs, the cuprous cyanide showed no polarization of anode or cathode yet gave smooth deposits.

Example I]! A 400-gallon acid-copper electrotyping bath used for commercial follows:

Copper sulfate crystals (CuSO4-5H:O) g./l 250 Sulfuric acid (66 86.) g./l 75 Cuprous cyanide g. l 0.1 Temperature C 30-40 Deposits from this betiitere remarkably'free cyanide. I ll RICHARD O. HULL e from trees at a current density of 150 A/s. f., the amount of waste copper being reduced about 75 per cent below that usually observed. Such small trees as were formed were flat and not objectionable.

The same bath composition used for electroforming produced deposits having exceptionally smooth surfaces free from nodules. anodes used in this bath wereremarkably free from objectionable anode sludge, in contrast with a similar bath not containing cuprous cyanide.

The same bath composition with the further addition of 2 mg./l. oi' glue produced smooth. hard deposits of excellent character. The same bath composition with the further addition of quinone, gave excellent, smooth deposits having almost no trees on the edges.

While I have shown certain illustrative baths it will be understood that without departing from the spirit of this invention one may readily produce numerous acid-copper baths employing cuprous cyanide as an addition agent.

I claim:

1. An aqueous acid-copper electrodepositing bath consisting essentially of copper sulfate and sulfuric acid, and containing not substantially less than about 0.1 gram per liter of cuprous cyanide.

2. In a process for electrodepositing copper from an aqueous acid-copper bath. the step comprising eflecting deposition from a bath which consists essentially of copper sulfate, sulfuric acid. and which issaturated with dissolved cuprous nrcminn 0.1mm.

m at. 19 5- It is hereby certified that error appears in the printed specification of the above nuiiiaered patent requiringv oorreotionae follows; Page 2, first column, line '50, Example I, last column thereof for "9.1" read --0.1'--; and that the said Letters Patent should. be read wiiii this correction therein that the same' confom to the record of the ease in the Patent Office.

Signed and sealed. this 18th day of'Deoenber, A. D. 1911.5.-

(Se a1) Leslie Erazer First Assistant Commissioner uf lltentl.

production was made up as The COPDCX porting strap or hook by means of which they may simply be hung in a bath. Awarding to a preferred practice of the invention equal parts with a little water and cast around a hook to make articles which look like the anodes of Blouch Patent 2,097,508. I

Compositions according to the present invention may be ofleredto the trade as mixtures of suitable copper compounds including appropriate amounts of cuprous cyanide. Alternatively and preferably, cupr'ous cyanide will simply be offered formed, with or without the aid of a binder. on a support by means of which it may be suspended in a plating bath. p

In order that my invention may be better understood reference should be had to the following illustrative examples:

Ezample I An acid-copper platingbath was made up as follows: I

Copper sulfate crystals (CuBO4-5H20) g./l 150 Sulfuric acid (66 Be.) g./l 50 Cuprous cyanide (CuCN) -g./l.. 9.1 Temperature .30.. 25-30 Copper deposits made from this bath were 01 greatly improved character over similar deposits made from a bath omitting the cuprous cyanide. The cuprous cyanide was introduced into the bath by suspending in it a plaster of Paris rod in which was incorporated about 50 per cent by weight of cuprous cyanide. During operation of the bath cuprous cyanide was dissolved as required, permitting the use of ,'high current densities of about 50 A/s.f. with elimination of roughness or nodular deposits in thicknesses up to .02 inch. The extreme smoothness and line texture of deposit made the deposits easy-to bull and suitable as a base coating for nickel plating. The inclusion of about one to two grams per liter of quinone as an organic addition agent was found desirable.

Example I! An acid-copper electroreflning bath was prepared as follows:

Copper sulfate crystals csarrrrosni cn-coaiiscnos.

I Patent Io. 237L289.

oi! cuprous cyanide andplaster of Paris are mixed i Deposits made from this bath in extreme thicknesses of one-half inch were smooth and dense. In contrast to gelatin or glue which polarise the anode or cathode as much as .19 volt at 15 A/s. f. as measured by the Haring cell with resultant increased power costs, the cuprous cyanide showed no polarization of anode or cathode yet gave smooth deposits.

Example I]! A 400-gallon acid-copper electrotyping bath used for commercial follows:

Copper sulfate crystals (CuSO4-5H:O) g./l 250 Sulfuric acid (66 86.) g./l 75 Cuprous cyanide g. l 0.1 Temperature C 30-40 Deposits from this betiitere remarkably'free from trees at a current density of 150 A/s. f., the amount of waste copper being reduced about 75 per cent below that usually observed. Such small trees as were formed were flat and not objectionable.

The same bath composition used for electroforming produced deposits having exceptionally smooth surfaces free from nodules. anodes used in this bath wereremarkably free from objectionable anode sludge, in contrast with a similar bath not containing cuprous cyanide.

The same bath composition with the further addition of 2 mg./l. oi' glue produced smooth. hard deposits of excellent character. The same bath composition with the further addition of quinone, gave excellent, smooth deposits having almost no trees on the edges.

While I have shown certain illustrative baths it will be understood that without departing from so the spirit of this invention one may readily produce numerous acid-copper baths employing cuprous cyanide as an addition agent.

I claim:

1. An aqueous acid-copper electrodepositing 5 bath consisting essentially of copper sulfate and sulfuric acid, and containing not substantially less than about 0.1 gram per liter of cuprous cyanide.

2. In a process for electrodepositing copper from an aqueous acid-copper bath. the step com- RICHARD 0. H

prising effecting deposition from a bath which consists essentially of copper sulfate, sulfuric acid. and which issaturated with dissolved cuprous cyanide. I

RICHARD O. HULL.

m at. 19 5- It is hereby certified that error appears in the printed specification of the above nuiiiaered patent requiringv oorreotionae follows; Page 2, first column, line '50, Example I, last column thereof for "9.1" read --0.1'--; and that the said Letters Patent should. be read wiiii this correction therein that the same' confom to the record of the ease in the Patent Office.

Signed and sealed. this 18th day of'Deoenber, A. D. 1911.5.-

(Se a1) Leslie Erazer First Assistant Commissioner uf lltdntl.

production was made up as The COPDCX 

